Composition Range of Morphotropic Phase Boundary and Electrical Properties of NBT-BT System

Abstract:

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(Na0.5Bi0.5)TiO3 (BNT) system ceramics are considered to be an excellent candidate for leadfree
piezoelectric ceramics. In this paper, (1–x)Na0.5Bi0.5TiO3-xBaTiO3 (x = 0.03 ~ 0.10) was synthesized
by conventional mixed-oxide technique. The powders were calcined at 950oC for 2 h and the pressed
disks were sintered at 1145oC for 2 h in air atmosphere. The phase structure was investigated by X-ray
diffraction technique (XRD). It is revealed that the morphotropic phase boundary (MPB) lies in a narrow
composition range of x=0.05–0.08 but not a unique composition (x = 0.055 or 0.06) as shown before [1-4].
The microstructures of the ceramics were investigated by scanning electron microscopic. In addition, the
piezoelectric and dielectric properties of this system were also investigated. It was indicated that both the
piezoelectric and dielectric properties are better with the compositions lie near the tetragonal phase within
the MPB than that whose compositions lie near the rhombohedral phase.

Abstract: A lead-free piezoelectric ceramic ternary system based on (Bi0.5Na0.5)TiO3 (BNT)-(Bi0.5
K0.5)TiO3(BKT)-BaTiO3(BT) near the morphotropic phase boundary (MPB) between the tetragonal
and rhombohedral phases has been investigated. The samples were prepared by a conventional
sintering technique. Piezoelectric properties, dielectric properties and microstructures of
BNT-BKT-BT lead-free piezoelectric ceramic were studied. The X-ray diffraction (XRD) patterns
show that the ceramics possess a single-phase perovskite structure. The measurements of
piezoelectric properties reveal that this system has a relatively high piezoelectric performance: the
piezoelectric constant d33 reached to 178pC/N and planar electromechanical coupling factor kp
enhanced to 0.325. The BNT-BKT-BT ternary system ceramics could be well sintered at 11500C with
a high-density ratio of more than 95% of the theoretical density.

Abstract: Lead-free piezoelectric ceramics lithium sodium potassium niobate (LixNayK1-x-y)NbO3
(LNKN100x/100y) have been synthesized by a conventional solid state process. The effects of MnO2
addition on the properties of (LixNayK1-x-y)NbO3(x=0.06, y=0.5)(LNKN6/50) ceramics were investigated.
It was found that a morphotropic phase boundary (MPB) between orthorhombic and tetragonal phases is
in the composition range 0.05

Abstract: In this work, preparation conditions and effect of ZrO2 doped BaFe0.5Nb0.5O3 ceramics were studied. Relationship between structure and dielectric properties was investigated. Single-phase cubic BFN powder was synthesized by solid-state reaction at 1200°C for 4 hours with heating and cooling rate of 5°C/min. Various amount of ZrO2 doped from 0.1 to 0.5 %weight were used for doping. After that BFN ceramics were formed via uniaxial pressing and sintered at 1300°C for 4 hours with heating and cooling rate of 5°C/min. Physical properties, microstructure, phase evolution and dielectric properties were studied to find out the optimum conditions for high voltage capacitor applications.

Abstract: Lead-free K0.5Na0.5NbO3-xwt% (0.4ZnO-0.6B2O3) ceramics were synthesized by conventional ceramics process. The co-doping of ZnO and B2O3 can decrease the sintering temperature of K0.5Na0.5NbO3 ceramics to 1000°C, and the samples show high relative density around 96%. X-ray diffraction (XRD) reveals that Co-doping of ZnO and B2O3 induces lattice distortion. Liquid phase is observed by scanning electron microscopy (SEM), which is resulted from the addition of ZnO and B2O3. The ceramics show better piezoelectric and dielectric properties with planar electromechanical coupling factor kp= 40.7%, piezoelectric constant d33=117pC/N, dielectric constant εT33/ε0=318.6, and loss tangenttanδ=0.034.